Parallel axis cylindrical microwave filter

Abstract

A microwave filter includes two resonant cylindrical cavities aligned in parallel along their longitudinal axes, with the cavities offset by one half the cavities' resonant wavelength with respect to one another. Signals to be filtered are coupled into a first, input, cavity through an input coupling and between the input cavity and a second, output, cavity through bridge and mainline couplings formed in a common cavity wall.

I claim: 
     
       1. A cylindrical multi-cavity microwave filter comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, where X is an integer greater than or equal to 3, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy between the magnetic field of the secondary resonance mode of the second resonator and the magnetic field of the primary resonance mode of the first resonator.   
     
     
       2. The cylindrical multi-cavity microwave filter of claim 1, wherein said output aperture is formed in the endwall of said second resonator at the opposite end from the input aperture of the first resonator. 
     
     
       3. The filter of claim 1, wherein said bridge aperture is located at a null of resonance modes of higher order than TE11X modes. 
     
     
       4. The filter of claim 1, wherein the cylinder ends which have neither input nor output apertures formed in the respective endwalls include temperature compensation flanges for accommodation of temperature compensation devices. 
     
     
       5. The filter of claim 1, wherein said at least one bridge aperture comprises at least two bridge apertures which are located at internal minima of the first resonator's said secondary resonance mode electric field strength. 
     
     
       6. The filter of claim 1, wherein both resonators support TE114 resonant modes and one of said at least one bridge apertures is located at the first internal electric field minimum from the input aperture. 
     
     
       7. A cylindrical multi-cavity microwave filter comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, where X is an integer greater than or equal to 3, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed one endwall, said resonators formed such that their longitudinal axes are parallel and they share a common wall along the longitudinal direction, both resonators arranged to support TE114 resonant modes,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   bridge apertures formed in said shared wall to couple energy between the magnetic field of the secondary resonance mode of the second resonator and the magnetic field of the primary resonance mode of the first resonator, said bridge apertures including a first bridge aperture located at the first internal electric field minimum from the input aperture, and a second bridge aperture located at the second internal electric field minimum from the input aperture.   
     
     
       8. The filter of claim 1, wherein both resonators support TE113 resonant modes and one of said at least one bridge apertures is located at the first internal electric field minimum from the input aperture. 
     
     
       9. The filter of claim 1, wherein said resonators form four resonant cavities. 
     
     
       10. A cylindrical cavity microwave filter comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy from the magnetic field of the secondary resonance mode of the second resonator to the magnetic field of the primary resonance mode of the first resonator, said resonators offset along their longitudinal axes from one another so as to align said apertures with preferred electric field intensities.   
     
     
       11. The cylindrical cavity microwave filter of claim 10, wherein an output aperture is formed at the opposite end of the second resonator from that of the input aperture of the first resonator. 
     
     
       12. A cylindrical cavity microwave filter comprising: a first right-cylindrical resonator for supporting primary and secondary TE114 mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE114 mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy from the magnetic field of the secondary resonance mode of the second resonator to the magnetic field of the primary resonance mode of the first resonator, said resonators offset along their longitudinal axes from one another so as to align the mainline aperture with a second-from-the-input-endwall electric field intensity peak and to align the bridge aperture with the first-from-the-input-endwall or -output-endwall electric field intensity minima.   
     
     
       13. The filter of claim 12, wherein said endwalls are offset by one half a TE114 wavelength. 
     
     
       14. A cylindrical cavity microwave filter comprising: a first right-cylindrical resonator for supporting primary and secondary TE113 mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy from the magnetic field of the secondary resonance mode of the second resonator to the magnetic field of the primary resonance mode of the first resonator.   
     
     
       15. A satellite communications transceiver, comprising: a multiplexer,   a plurality of right cylindrical resonant cavity transmitting filters connected to filter input signals and to provide filtered output signals to respective inputs of said multiplexer which combines said filtered signals into a multiplexed signal, and   a transmitting antenna connected to receive the filtered, multiplexed signals from said multiplexer and to transmit said multiplexed signal, each of said filters comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy from the magnetic field of the secondary resonance mode of the second resonator to the magnetic field of the primary resonance mode of the first resonator.     
     
     
       16. The communications transceiver of claim 15, further comprising: a receiving antenna connected to receive a radio frequency signal,   a plurality of receiving filters connected to filter said received signal, each of said receiving filters comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that they are non-coaxial, their longitudinal axes are parallel and they share a common wall along the longitudinal direction,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   at least one bridge aperture formed in said shared wall to couple energy from the magnetic field of the secondary resonance mode of the second resonator to the magnetic field of the primary resonance mode of the first resonator, and     a plurality of amplifiers connected to receive said filtered output signals from respective receiving filters, to amplify said signals, and to transmit said signals to said transmitting filters.   
     
     
       17. The transceiver of claim 16, wherein said at least one bridge aperture is located at a null of resonance modes of higher order than TE11X modes. 
     
     
       18. The transceiver of claim 17, wherein the cylinder ends which have neither input nor output apertures formed in the respective endwalls include temperature compensation flanges for accommodation of temperature compensation devices. 
     
     
       19. The transceiver of claim 18, wherein said at least one bridge aperture comprises at least two bridge apertures which are located at internal minima of the first resonator's said secondary resonance mode electric field strength. 
     
     
       20. The transceiver of claim 16, wherein both resonators support TE114 resonant modes and one of said at least one bridge apertures is located at the first internal electric field minimum from the input aperture. 
     
     
       21. A satellite communications transceiver, comprising: a multiplexer,   a plurality of right cylindrical resonant cavity transmitting filters connected to filter input signals and to provide filtered output signals to respective inputs of said multiplexer which combines said filtered signals into a multiplexed signal,   a transmitting antenna connected to receive the filtered, multiplexed signals from said multiplexer and to transmit said multiplexed signal,   a receiving antenna connected to receive a radio frequency signal,   a plurality of receiving filters connected to filter said received signal, and   a plurality of amplifiers connected to receive said filtered output signals from respective receiving filters, to amplify said signals, and to transmit said signals to said transmitting filters, each of said transmitting and receiving filters comprising: a first right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said resonator having endwalls at either end and an input aperture formed in one end wall,   a second right-cylindrical resonator for supporting primary and secondary TE11X mode electromagnetic resonances, said second resonator having endwalls at either end and an output aperture formed in one endwall, said resonators formed such that their longitudinal axes are parallel and they share a common wall along the longitudinal direction, both resonators arranged to support TE114 resonant modes,   a mainline aperture formed in said shared wall to couple energy from the magnetic field of a secondary resonance mode of the first resonator to the magnetic field of a primary resonance mode of the second resonator, and   bridge apertures formed in said shared wall to couple energy between the magnetic field of the secondary resonance mode of the second resonator and the magnetic field of the primary resonance mode of the first resonator, said bridge apertures including a first bridge aperture located at the first internal electric field minimum from the input aperture, and a second bridge aperture located at the second internal electric field minimum from the input aperture.     
     
     
       22. The filter of claim 16, wherein both resonators support TE113 resonant modes and one of said at least one bridge apertures is located at the first internal electric field minimum from the input aperture. 
     
     
       23. The transceiver of claim 16, wherein said resonators form four resonant cavities.